Can a subscription’s amount be edited directly?
Short answer
No. The amount, like every billing rule, comes from the offer. To charge a different amount, move the subscription to another offer at the next billing date, or add a one-off charge for an extra amount. Changing the offer itself creates a new version that applies to every subscription on it.
In detail
No.
The offer holds the terms
A subscription has no amount of its own: it reads it from its offer at each billing date.
Move to another offer
The subscription switches at the next billing cycle, with no proration, and keeps its payment token.
Add a one-off charge
An extra amount is charged on the same subscription and joins its order history.